Voltage level-shifting circuits provide interfaces between circuit systems at two different voltage domains. Different voltage domains are often necessary for consumer electronic integrated circuit systems. A first integrated circuit may be embodied, for example, as a digital controller that carries digital voltage signals that vary between a first set of voltages, for example, ground (0V) and 1.8V. A second integrated circuit may be embodied as a charge coupled device (CCD) and may require discrete operating voltage signals that vary between a second set of voltages, for example, −8V and 15V. A level-shifting circuit may convert signals from the domain of the first integrated circuit to the domain of the second integrated circuit.
Level-shifting circuits have been used to perform voltage conversion between such domains. In one application, the level-shifting circuit may be implemented as a two-stage circuit to accomplish the conversion between a 0V to 1.8V range and a −8V to 15V range. A first stage converts the input range to an intermediate 0V to 15V range, and then a second stage converts the intermediate range to a final −8V to 15V range.
The two-stage implementation has been accomplished using static level shifter circuits, which are area intensive. As the magnitudes of the voltage ranges diverge, devices within the level-shifters must become larger, which increases the silicon area consumed by such devices. Further, the known implementations employ a separate level shifter circuit for each output signal line extending between the two domains. As system designs evolve and the number of interface signals increase, the area consumption issue scales in kind.
Accordingly, there is a need in the art for a level-shifter system that converts signals from a low voltage domain to a high voltage domain and minimizes area.